1. Technical Field
The present invention relates generally to the data processing field and, more particularly, to a method, system and computer program product for tracking changes in a Level 1 data cache directory in a processor in a data processing system.
2. Description of Related Art
A processor, such as a microprocessor, in a data processing system typically employs a built-in Level 1 (L1) memory cache to reduce the average time to access memory. An L1 cache includes both data and instructions and is effective because many programs tend to access the same data or instructions over and over, and by maintaining as much of this information as possible in the L1 cache, the processor may often avoid having to access the slower main memory of the data processing system.
An L1 data cache directory (L1 DCache directory) as used in current systems consists of 32 entries×16 way associative×about 50 bits of address and miscellaneous information (32×16=512 entries×50 bits). This design results in substantial time windows and requires an extra copy of the L1 DCache directory to properly maintain the directory and to avoid losing data due to changes in directory allocation. This extra L1 DCache directory requires a great deal of area in the L1 DCache.
It would, accordingly, be desirable to provide a mechanism for tracking changes in a Level 1 data cache directory in a processor in a data processing system that will eliminate time windows from the design and also eliminate the need for an extra L1 DCache directory.